The Food and Drug Administration warned Kellogg Co. about bacteria and substandard production procedures at a food manufacturing plant in Augusta, Ga., a setback for the food company that has tried to mend a supply chain that has faced several major recalls recently.

In a letter posted to its website on Tuesday, the FDA said it found listeria in the facility, including on "food contact" surfaces. While the FDA warned that items like cookies may not support the growth of listeria, the FDA cautioned that the lack of sanitation may allow for food to become "contaminated with filth."

The Food and Drug Administration found traces of listeria at a Kellogg Co. bakery in Augusta, Ga., during an inspection earlier this year.

In a letter released Tuesday, regulators say that the pathogen was found in several spots along the production line that comes in direct contact with food. The FDA also noted other problems at the plant such as insects near areas where food is located.

Kellogg said it has undertaken a number of aggressive actions to address the concerns and is confident in the safety of its food.

The company, based in Battle Creek, Mich., makes a variety of Keebler and Famous Amos cookies at the Augusta plant.

Eggo Production

Kellogg’s cookies are baked at a temperature high enough to kill any listeria present, according to Robert Gravani, a food science professor at Cornell University in Ithaca, New York. The lack of an FDA product recall suggests that listeria was not found in the cookies, he said. FDA spokeswoman Tamara Ward declined to comment on a potential recall.

Listeria is a bacterium found in prepared foods and soil that can cause a serious infection in humans called listeriosis. It is particularly harmful to pregnant women, the young, the elderly, and people with weak immune systems, according to the FDA’s website.

Kellogg, the largest U.S. maker of breakfast cereals, fell 45 cents to $54.96 at 4 p.m. in New York Stock Exchange composite trading. The shares have gained 7.6 percent this year.

The agency didn’t find the pathogen in any Kellogg foods, but on and around conveyor belts in the production line. The agency said:

“We note that although your finished product cookies may not support the growth of L. monocytogenes, the positive environmental swabs are indicators of insanitary conditions in your facility and demonstrate a failure of cleaning and sanitation operations that may allow for contamination of foods with filth or pathogens.”

Speaking of filth in the factory, the agency also took issue with pooling water that was observed dripping into an open mixer bowl and flies swarming near food mixers.

This isn’t the first time listeria and Kellogg have been in headlines. Inspectors found the food-poisoning organism in 2009 in a Kellogg plant in Atlanta, Ga., prompted by contaminated Eggo buttermilk waffles—the FDA sent Kellogg a warning letter back then too.

FDA said it would determine at its next inspection whether the steps taken by Kellogg are sufficient. In the meantime, FDA gave the company 15 working days to respond to the warning letter with documentation.

"We have undertaken a number of aggressive action to address their (FDA) concerns, including compressive cleaning and extensive testing, and have confidence in the safety of our food," said Kris Charles, Kellogg spokeswoman.

Listeria can be very difficult to eradicate once the pathogen becomes takes hold inside a food plant. Maple Leaf Foods in Toronto found that out three years ago when its failure to eradicate Listeria led to a nationwide outbreak linked to deli meats that killed 22 mostly elderly Canadians.

Two years ago, local development authorities in Georgia provided $30 million in tax-exempt bond financing for improvements at the Kellogg's facility in Augusta. The Battle Creek, MI-based company also made fairly recent investments in $5 million worth of equipment relocated to the former Murray's Biscuits plant.

Kellogg Company sales totaled more than $12 billion last year. It has manufacturing facilities in 18 countries and markets products in more than 180 counties. Problems at some of its U.S. plants last year led to a shortage of its popular Eggo frozen waffles and several popular cereals had to be recalled over packaging problems.